Re: need some info
If you are rebarrelling or rechambering a Ruger No 1, the extractor is made to handle the original cartridge whether rimmed or rimless. It can be changed but generally folks simply go with the same cartridge base as the original round, so there is no problem.
Just FWIW, there are very few semi-rimmed rifle cartridges; the only one I can think of offhand is the 7.7 Japanese round for the Type 99 Hotchkiss strip-fed machinegun. (The Type 99 rifle uses a rimless 7.7 cartridge.) There are a few modern cartridges with rebated rims, notably the .284 Winchester and the .338 Remington Ultra Mag.